As this type technique according to the background art, there is a technique disclosed in Patent Literature 1. In this Patent Literature 1, disclosed is a working machine such as a hydraulic excavator provided with a body including an upperstructure, and a working device attached to the upperstructure, the working device including a boom which is connected to the upperstructure so as to be rotatable in an up/down direction, an arm which is connected to a distal end of the boom so as to be rotatable in the up/down direction, a boom cylinder which drives the boom, and an arm cylinder which drives the arm. In this Patent Literature 1, disclosed is a configuration in which a hydraulic circuit device provided in the hydraulic excavator, that is, a hydraulic drive device includes a first hydraulic pump and a second hydraulic pump which supply pressure oil for operating the boom cylinder and the arm cylinder respectively, a first boom directional control valve connected to the first hydraulic pump and in parallel with a second arm directional control valve so as to control a flow of the pressure oil supplied to the boom cylinder, the second arm directional control valve connected to the first hydraulic pump and in parallel with the first boom directional control valve so as to control a flow of the pressure oil supplied to the arm cylinder, a second boom directional control valve connected to the second hydraulic pump and in parallel with a first arm directional control valve so as to control a flow of the pressure oil supplied to the boom cylinder, and the first arm directional control valve connected to the second hydraulic pump and in parallel with the second boom directional control valve so as to control a flow of the pressure oil supplied to the arm cylinder.
Though not shown in the aforementioned Patent Literature 1, as a hydraulic drive device provided in a working machine such as a hydraulic excavator, it has been hitherto known that a fixed throttle is provided on the upstream side of an arm directional control valve which will serve as the low pressure side during combined operation of boom raising and arm crowding, in consideration of controllability during the combined operation. As this type technology according to the background art, there is a technique disclosed in Patent Literature 2.
In addition, though not shown in the aforementioned Patent Literature 1, as a hydraulic drive device provided in a working machine such as a hydraulic excavator, there has been hitherto known a hydraulic drive device provided with a regenerative circuit having a throttle which narrows a return pipe line so that oil discharged from a rod chamber of an arm cylinder can be regeneratively supplied to a bottom chamber during arm crowding operation for moving down an arm by its own weight. As this type technology according to the background art, for example, there is a technique disclosed in Patent Literature 3.